In the automatic testing of integrated circuits and other electronic devices, special device handlers have been used which place the device to be tested in position. The electronic testing itself is provided by a large and expensive automatic testing system which includes a test head which connects to and docks with the device handler. The test head uses high speed electronic timing signals so that the electronic circuits must be located as close as possible to the device under test. Accordingly, the test head is densely packaged with electronic circuits in order to achieve the high speed testing of the sophisticated devices.
A manipulator or positioner, movable along a support structure, carries the test head to the desired location at which the test head is positioned to connect to and dock with the device handler. The test head is attached to the positioner by means which permit the test head to be pivoted about two orthogonal axes in addition to the axis of the support structure through which the positioner moves.
A major problem is connecting a heavy cable, extending from a cabinet containing part of the automatic testing system, into the test head which itself is movable to a desired location and into a desired position. Provision must be made for the heavy cable to move with the test head.
One arrangement used in the past has involved passing the cable through the mechanism by which the test head is attached to the positioner. This mechanism is arranged to permit pivotal movement of the test head about a horizontal axis extending through the mechanism and is in line with the cable. The design of this mechanism is particularly complex and expensive when it is adapted for passage of the cable through it to the test head.
In another arrangement, the cable is slung beneath the test head in such a way that it connects into the test head in the side of the test head opposite from the mechanism by which the test head is attached to the positioner. While this approach avoids a complex and expensive mechanism by which the test head is attached to the positioner and the cable is connected to the test head, the cable, hanging beneath the test head to beyond the side of the test head for a number of orientations of the test head, gets in the way of the operator of the testing system. Also, the cable must be lengthened because it extends completely across the bottom of the test head for certain orientations of the test head.
In yet another arrangement, the cable is passed through a cable housing to which the test head is attached for pivotal movement of the test head relative to the cable housing. The cable housing, in turn, is attached to the positioner for pivotal movement of the cable-housing and the test head about a horizontal axis. Although the test head is mounted so that it can be pivoted about two orthogonal axes, the center of gravity of the test head is displaced from the horizontal axis about which the cable housing and test head pivot. As a result, the test head which, as indicated above, is very heavy must be counterbalanced, thereby adding complexity and cost to the means by which the test head is attached to the positioner.